Field of the Invention
The present invention generally relates to mobile communication networks.
In a general way, mobile communication networks are subject to standardisation; therefore details on such networks can be found in the corresponding standards, published by the corresponding standardisation bodies.
Description of the Prior Art
Such networks usually comprise a Radio Access Network (RAN) and a Core Network (CN), and usually have a hierarchical architecture.
For example, as recalled in FIG. 1, in GSM (respectively UMTS), RAN nodes such as Base Station (BS) (respectively NodeB) are connected to RAN nodes such as Base Station Controller (BSC) (respectively Radio Network Controller (RNC)) in a hierarchical way. In the same way, RAN nodes such as BSC (respectively RNC) are connected in a hierarchical way to CN nodes such as Mobile Switching Center/ Visitor Location Register (MSC/VLR) (for a Circuit-Switched (CS) domain) or Serving GPRS Support Nodes (SGSN) (for a Packet-Switched (PS) domain), in turn connected in a hierachical way to other CN nodes such as Gateway Mobile Switching Center (GMSC) for CS domain, or Gateway GPRS Support Node (GGSN) for PS domain. RAN nodes such as BS/NodeB communicate with Mobile Stations (MS) (respectively User Equipement (UE)), not specifically illustrated, over a radio interface. CN nodes such as GMSC/GGSN communicate with other networks, not specifically illustrated.
Usually, CN nodes such as MSC/VLR and/or SGSN are in charge of a number of functions, including in particular a Mobility Management (MM) function and a Paging Coordination (PC) function.
The Mobility Management (MM) function includes, for MS/UE which are not actively engaged in a connection (in particular MS/UE in idle mode) keeping track of MS/UE location with the accuracy of an area (usually called Location Area (LA) or Routing Area (RA)) made of a set of cells, and checking user access rights on said LA/RA basis, using subscription data held in a subscriber database such as Home Location Register (HLR) or Home Subscriber Server (HSS).
The Paging Coordination (PC) function includes contacting the appropriate RAN nodes for the sending of paging messages over the last LA/RA where a MS/UE has been registered, when there is a need to reach the MS/UE, such as for example for an incoming call or session.
In each cell, the corresponding LA/RA is broadcast on the radio interface so that a MS/UE moving from one cell to another cell can know whether the LA/RA has changed or not. When the LA/RA has changed, MM procedures (such as Location Update procedures) are carried out for registering the MS/UE in the new LA/RA.
LA/RA configuration is important for network optimisation, in particular for optimising the amount of signalling traffic in the network, in particular for Mobility Management and Paging Coordination functions. LA/RA configuration is generally performed via Operation & Maintenance (O&M) operations.
In a hierarchical architecture as recalled for example in FIG. 1, such LA/RA configuration usually comprises two operations: the mapping between LA/RA and BSC/RNC nodes is configured by O&M in the CN, and the set of cells belonging to a given LA/RA is configured by O&M in the BSC/RNC.
Each time there is a change in the RAN configuration, such as for example when a new BS/NodeB is added or removed, the RAN operator has to configure the RAN nodes (BSC/RNC) accordingly. This has no impact on the CN configuration, i.e. the CN operator does not have to configure the CN nodes (MSC/SGSN) accordingly, if at least one cell controlled by the BSC/RNC is in an existing LA/RA. In other words, while the configuration of RAN nodes may change relatively frequently, in the above-recalled hierarchical architecture CN nodes can be configured on a permanent or semi-permanent basis.
Now, there is an evolution of the architecture of such networks towards future generation networks. An example of an architecture of such future generation networks is illustrated in FIG. 2. The trend is to go from the above-recalled hierarchical architecture to a “flat” architecture, or in other words to reduce the number of “intermediate” nodes (such as BSC/RNC in the above-recalled hierarchical architecture), in order to reduce setup delays and user plane latency. In particular, the trend is to go from four nodes such as GGSN-SGSN-BSC/RNC-BS/NodeB, to two nodes such as ASGW (Access System GateWay)-ENB (Enhanced NodeB), in the user plane and possibly in the control plane as well. The MM function and the PC function (in the control plane) can be hosted in the ASGW or in a separate node (such as the node noted MM/PC in FIG. 2). The PC function can be located in the CN or in the RAN. Generally, the network entity in charge of MM function is called Mobility Management Entity (MME), and the network entity in charge of PC function is called Paging Coordination Entity (PCE), regardless of the physical network node(s) where these functions can be located. Nodes such as ENB, ASGW, MME, PCE are interconnected by an IP-based transport network or backbone.